1. Field of the Invention
This invention relates to a process for the production of an alcoholic solution of an ethyl or butyl half-ester of a copolymer of maleic anhydride and a methyl vinyl ether, and, particularly, to a process for making an ethanol solution of an ethyl or butyl half-ester of maleic anhydride and methyl vinyl ether at a high solids content and low viscosity.
2. Description of the Prior Art
M. Tazi, in U.S. Pat. No. 4,939,198, described a solution feed, solution polymerization process for the production of alcoholic solutions of alkyl half-esters of copolymers of maleic anhydride and an alkyl vinyl ether using acetone as solvent. The process involved precharging a reactor with a molar excess of an alkyl vinyl ether, preferably with some acetone, then feeding maleic anhydride as a solution in acetone into the precharged reactor, solution polymerizing the reactants in the presence of a free radical initiator, half-esterifying the resultant solution with an alkanol, and solvent exchanging the alkanol for acetone. The products obtained contained half-esters of low viscosity and high solids content for use in non-aerosol, pump hair sprays.
Goertz, in U.S. Pat. No. 4,908,413, described a similar process in which a portion of the monomer reactants were dissolved initially in precharged acetone as solvent, and the remainder was metered in over several hours. The maleic anhydride monomer was introduced as a solution in acetone and the alkyl vinyl ether as the liquid itself. The copolymer solution was esterified by addition of ethanol to the copolymer solution at 56.degree. C. resulting in a viscous pasty heterogeneous mass because the copolymer was insoluble in ethanol. After stirring for an extended period of time, the mass became more homogeneous. Then distillation was begun under reduced pressure with additional ethanol being added whenever the limit of stirrability was reached.
These and other processes for making such products, however, have certain disadvantages or limitations, which are desired to overcome in this invention, in order to provide a more commercially effective process.